1. Field of the Invention
This invention relates to pressurized dispenser packages, such as aerosol packages, wherein the product to be dispensed and the pressure-generating media, i.e. the propellant, are maintained in isolation through separation on opposite sides of a barrier. An aerosol package of this type is generally referred to as a xe2x80x9cbarrier packxe2x80x9d aerosol package.
2. Description of the Prior Art
Aerosol barrier packs of the prior art have been of at least three general types. In the piston-type barrier pack the barrier is a piston-like component that is mounted in the container in sliding relation to the inside surface of the container. The product to be dispensed is disposed on the valved side of the piston and the propellant, which generates pressure within the container, is on the opposite of the piston. In Aerosol Handbook, Second Edition, 1982, there is described a piston-type aerosol dispenser marketed by American Can Company under the trade-name xe2x80x9cMira-Floxe2x80x9d. In the Mira-Flo dispenser the piston skirt is designed to seal against the sides of the container to prevent the propellant gas from passing into the product chamber on the other side of the piston. Actuation of the aerosol discharge valve causes a reduction in pressure in the product chamber thereby resulting in the pressure in the propellant chamber urging the piston toward the discharge valve. Examples of a piston-type barrier pack are described in U.S. Pat. Nos. 3,022,923, 3,756,476 and 3,929,132.
In a second type of aerosol barrier pack, a flexible, collapsible bag is affixed within the container opening either to the aerosol discharge valve or to the bead of the container opening. The Continental Can Company in the late 1960""s introduced an aerosol barrier dispenser known as the xe2x80x9cSepro-Canxe2x80x9d. The Sepro-Can includes an interior plastic product bag having an opening that is attached to the valve opening at the top of the container. The side walls of the bag extend along the side walls of the container and are pleated like an accordion so the bag can collapse inward and upward under the influence of pressure in the remainder of the container as the bag is emptied. Patents which illustrate a barrier pack of the second type are set forth in U.S. Pat. Nos. 3,788,521, 3,896,970 and 4,067,499. Modifications of barrier packs of the second type include attaching the bag to the side wall of the container or to the joint formed between the side wall of the container and the top of the container.
A third type of prior art barrier pack is an unfolding cup-shaped barrier wherein the barrier has an outer wall terminating in a sealing flange, said outer wall being disposed contiguous to the inner wall of the container. The inner wall of the barrier is initially folded within the outer wall, the inner wall terminating in an end closing portion. The barrier is contained in a valved aerosol container and sealed at the joint formed between the sidewall and the bottom end closure of the container. Product is admitted through the valved opening of the container and propellant through a port in the bottom end closure of the container. Actuation of the valve reduces the pressure in the product compartment and results in the inner wall of the barrier unfolding from within the outer wall of the barrier to advance and thereby urge the product toward the discharge valve. A patent which illustrates the third type of prior art barrier pack is U.S. Pat. No. 3,109,463.
A problem with the piston-type barrier pack of the first type is the imperfect seal between the side skirt of the piston and the side wall of the container which allows propellant to seep into the product with consequent discharge of propellant during product discharge as well as contamination of the product with propellant. Also, it is not uncommon for aerosol containers to be dented and thus lose their true circumferential shape, with the consequence that the piston is incapable of axial movement within the container past the aberrant configuration.
A problem with barrier packs of the second type wherein the barrier is affixed to the valve or valve opening of the container is that the barrier collapses in a manner to cause pocketing of the product within the collapsible barrier with consequent undesirable diminution of the evacuation of the product from the container.
In the third type of prior art barrier pack described herein, the unfolding cup-shape barrier does not advance progressively and uniformly against the inner wall of the container but tends to pocket and entrap product against the wall or within pockets formed in the barrier itself as it unfolds. Attempts to solve these problems have included adding an additional rigid piston to the end-closing portion of the inner wall, or adhering the outer wall of the barrier in peelable fashion to the inner wall of the container. Generally, barriers of the third type can be difficult to form, as well as to insert into and seal with the container.
There is, therefore, a need for a flexible product/propellant barrier for an aerosol container that is easy to manufacture and ship, that is easy to insert into and seal to the container, that prevents leakage of the fluids from one compartment to the other compartment, and that does not pocket and therefore preclude evacuation of significant amounts of the product to be discharged.
The present invention relates to an improvement in the third type of barrier pack. In its broadest aspect, the present invention concerns a unitary flexible and expandable barrier of phallic configuration for use in a plural-zoned, valved pressure container wherein the barrier has a shaped spatial form having sufficient rigidity to maintain its shape prior to insertion into and use in a plural-zoned, valved pressure container. The barrier comprises a flexible and expandable wall portion, the free terminal end of the flexible and expandable wall portion forming a sealing means and the terminus of the flexible and expandable wall portion distal to the sealing means extending into a central piston region that closes the barrier. The wall portion is steeply frusto-conical in shape. The wall portion of the barrier of this invention has a first portion which terminates in the central piston region and a second portion which terminates at its free end in the sealing flange. Further, when the barrier is top sealed within a container and when the second portion is substantially thicker than the first portion, the wall portion of the barrier is, during product discharge from the container, sufficiently flexible and expandable to permit the wall portion and its central piston region to move in an axially upward direction under the influence of propellant pressure to more or less fold within itself.
When the aforedescribed barrier is bottom sealed in the container, the wall portion of the barrier is, during product discharge from the container sufficiently flexible and expandable to permit the wall portion and its central piston region to move in an axially upward direction under the influence of propellant pressure to more or less assume a phallic configuration.
Still further, the wall portion of the barrier has sufficient flexibility and expandability to extend outwardly, under the influence of propellant pressure, in the case where the barrier is bottom sealed, and under the influence of product pressure in the case where the barrier is top sealed, to substantially conform to the inner surface of the container.
As noted above, the wall portion of the barrier of this invention may be viewed as having a first upper wall portion terminating in the central piston region and a second wall portion terminating in the free-end sealing means.
In the case where the barrier of phallic configuration is bottom sealed to the container, when the second wall portion is sufficiently thicker and more rigid than the first wall portion, the first wall portion will invert within the second wall portion under the influence of product pressure during filling of the container with product. During evacuation of the product in a bottom sealed barrier having a thicker and more rigid second wall portion, the second wall portion will conform to the shape of the inside surface of the container and the first wall portion will move axially toward the container opening and ultimately assume a more or less phallic configuration, i.e. the configuration of the barrier prior to product filling of the container. The first wall portion will also conform to the shape of the inside surface of the container.
Again, in the case of bottom sealing, but where the first and second wall portions are of comparable thickness and rigidity, during product filling of the container, the barrier throughout its length will crush and not assume the inversion configuration of the first wall portion into the second wall portion. During evacuation of product from a bottom-sealed barrier having comparable first and second wall portions, the barrier will ultimately assume the initial phallic configuration and will then conform to the inside surface of the container.
In the case where the barrier is top sealed to the container, when the second wall portion is thicker and more rigid than the first wall portion, the first wall portion will invert within the second wall portion under the influence of propellant pressure during discharge of product. Again, with a top sealed barrier and in the instance where the first and second wall portions of the barrier are of comparable thickness and rigidity, evacuation of product will cause the barrier to assume a non-descript, crumpled configuration as the barrier moves toward the valve of the container under the influence of propellant pressure. However, the non-descript, crumpled configuration still permits excellent evacuation of product from the barrier.
By virtue of having sufficient rigidity to maintain its shape prior to insertion into the container, as well as the presence of the tapered wall portion, the barrier of the present invention is very easily insertable into the container. By virtue of the tapered contour of the wall portion of the barrier, the barrier is nestable with like barriers for convenience and cost savings in shipping. Further, the nesting facilitates fast and simple machine feeding of stacked barriers sequentially into the containers.
In a preferred form of the invention the sealing flange is thicker than the first and second wall portions; the first wall portion also is of slightly less length than the second wall portion; and the sealing means is a radially extending flange which acts as a gasket between the container and the respective top or bottom closures of the container. The central piston region also may be thicker than the first wall portion.
A particularly advantageous material for barriers is polyethylene terephthalate (PET). Where permeation across the barrier is a concern, the barrier of the present invention may utilize a unitary multi-layer configuration. Such multi-layer configurations, their materials of construction and their manufacture, are well known to those skilled in the art. Generally, in a three-layer system, the inner layer is a material that prevents transport of propellant and product therethrough and the outer layers are inert to the propellant and product.